Thomil, the Destroyer is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

+2: Create a 2/2 black Zombie creature token. 0: You may sacrifice a creature. If you do, add . −5: Create a Lord of the Pit token. (It's a 7/7 Demon creature with flying, trample, and "At the beginning of your upkeep, sacrifice another creature. If you can't, this token deals 7 damage to you.") Thomil, the Destroyer can be your commander.